<!DOCTYPE html>
<html lang="en">

<head>
    <meta charset="UTF-8">
    <meta name="viewport" content="width=device-width, initial-scale=1.0">
    <title>Document</title>
    <script src="https://cdn.staticfile.org/react/16.4.0/umd/react.development.js"></script>
    <script src="https://cdn.staticfile.org/react-dom/16.4.0/umd/react-dom.development.js"></script>
    <script src="https://cdn.staticfile.org/babel-standalone/6.26.0/babel.min.js"></script>
</head>

<body>

    <div id="example"></div>
    <script type="text/babel">
        class Clock extends React.Component {
            constructor(props) {
                super(props);
                this.state = { date: new Date() };
            }

            render() {
                return (
                    <div>
                        <h1>Hello, world!</h1>
                        <h2>现在是 {this.state.date.toLocaleTimeString()}.</h2>
                    </div>
                );
            }
        }

        ReactDOM.render(
            <Clock />,
            document.getElementById('example')
        );
    </script>

</body>

</html>